You burn a candle one evening and in the morning find a grey ring clinging around the wall of the cup. This happens to almost everyone who uses candles, and it almost always begins with a very small detail few people notice: the length of the wick.
A candle flame needs exactly a certain amount of liquid wax to burn completely. When the wick is long, the flame draws up more wax than it can burn in time, and that surplus escapes as black soot, then settles on the wall of the cup with the heat. A wick trimmed to about five millimetres gives a small, steady flame that burns neatly, and the wall of the cup stays clear.
Draught is the second cause. A current of air from a window, a fan or an air conditioner makes the flame sway back and forth, and each sway is an incomplete burn. That is why we still advise standing the candle somewhere sheltered from draughts, well away from any current blowing directly at it, and that way the scent also stays in the room longer.
How to put it right in a few minutes
Put the candle out and wait until the cup has cooled completely. Wipe the wall of the cup with a dry paper towel, dampening it a little for the difficult spots. Then trim the wick to about five millimetres, lift off the blackened wick tip lying on the wax surface, move the cup somewhere sheltered from draughts, and light it again.
If the wax surface has sunk deeply around the wick and the wick sits lower than the surface, pour a little of the wax off the top onto paper, pull the wick up and trim it. The flame will settle back in its proper place.
A little about our candle jars
ZUNGZA candles use a full cotton wick and soy wax we blend ourselves; the wax keeps its natural colour, so you see every change on the wax surface clearly. A cooled candle surface is usually a little off in colour, speckled in places with small holes, and this is normal for a soy wax candle rather than a sign of smoke.
Black soot is another matter. Soot is a question of the wick and of the draught, and you can deal with it entirely by two small movements before each lighting.
A few questions you often send us
How much wick is right to trim
About five millimetres measured from the wax surface, trimmed before each burn.
Can the wall of the cup be cleaned once it has blackened
It can; wait for the cup to cool then wipe it with a dry or damp paper towel, and light it again with a trimmed wick.
Does blowing a candle out create smoke
Blowing makes more smoke rise. Use the jar lid with the cinnamon cuprange, or press the wick down into the melt pool and stand it up again, and there will be almost no smoke.
We write in more detail about the rhythm of burning in the instructions for use, and if you have other questions the frequently asked questions page has many more entries.